Internal-combustion engine



FIG. 1 is a front view of an internal-combustion engine, showing our new design;

FIG. 2 is a back view thereof;

FIG. 3 is a left view thereof;

FIG. 4 is a right view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a perspective view thereof. 

The ornamental design for an internal-combustion engine, as shown and described. 